Power tools of the type under consideration include hammer drills, for example, which are electric or battery powered and includes two modes of operation: a rotation mode and a rotation-hammer mode. A manually operable selector lever enables the hammer drill to be selectively operated in one of the two modes by disengaging a hammer mechanism when the selector lever is placed in a first position and engaging the hammer mechanism when the selector lever is placed in a second position.
When the selector lever is placed in the first position, the power tool operates in a rotation action mode. This mode is selected for rotating a tool element, such as a drill bit, in order to drill a hole in material such as wood or plaster.
When the selector lever is placed in the second position, the power tool operates in a rotation-hammer action mode in which a hammer action works in combination with rotation to rotate and hammer a tool element. One well-known use of the simultaneous rotation and hammer action of the rotation-hammer mode is to drill a hole in resistant material such as steel or concrete. When the power tool operates in the rotation-hammer mode, the operator must exert a pressing force or contact pressure to the tool element positioned in the chuck in order to actuate the hammer mechanism.
The manually operable selector lever determines operation of such hammer drills having the dual function of rotation mode and rotation-hammer mode. Operators of these dual function power tools often find it necessary to perform work that requires the tool to be operated solely in a hammer action mode, such as chiseling. However, a sole hammer action mode is not available in such dual function power tools. Although power tools, such as rotary hammers, exist with three modes of operation: a rotation mode, a rotation-hammer mode, and a hammer or chiseling mode, these power tools are more expensive than the dual mode power tools discussed above. An object of the present invention is to enable dual function power tools, such as hammer drills having a rotation mode and a rotation-hammer mode, to be operated in a hammer only mode.
The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Inventions with the accompanying drawings described below.